Post-nuclear-war dramas centering on a small group of survivors now constitute an entire genre in science-fiction films       All of them, in some way or another, can be traced back to this seminal film from 1951 in which five people deal with the possibility they are the only human beings left alive on the planet      　　While most of the later movies exploited this possibility for B-movie thrills, Five adopts a quiet, contemplative tone which some may find dull but which thoughtful viewers are more likely to find, for want of a better word, haunting       There is something about this movie which gets under the skin and which lurks in the corners of the mind long after it's over